Apparatus and methods for monitoring health of semiconductor process systems

ABSTRACT

Disclosed are apparatus and methods for monitoring an operation parameter of a process tool, independently of a process system recipe, are provided. In one embodiment, the behavior of a process device as it transitions between different states is monitored for a single cycle of operation or over time to detect trends that indicate a potential failure of the process device. When a trend that indicates a potential failure is detected, an alarm is generated. In one implementation, the time for reaching a particular stage of operation may be repeatedly monitored over a plurality of device cycles. For example, the time to open a valve or door may be monitored. In another example, the time for reaching a stable phase of gas flow after a ramping stage has commenced is monitored. When the time for reaching a particular stage begins to decline by a predetermined amount, an alarm may be generated.

CROSS REFERENCE TO RELATED PATENT APPLICATION

This application is a continuation of and claims priority of U.S. patentapplication Ser. No. 11/473,890, entitled APPARATUS AND METHODS FORMONITORING HEALTH OF SEMICONDUCTOR PROCESS SYSTEMS, filed 23 Jun. 2006by Jeffery William Achtnig et al., which application is incorporatedherein by reference in its entirety for all purposes.

BACKGROUND OF THE INVENTION

The present invention relates generally to processing of semiconductorwafers in a plurality of processing systems. More specifically, itrelates to automatically monitoring the operation of such processingsystems.

Generally, the industry of semiconductor manufacturing involves highlycomplex techniques for fabricating integrating circuits fromsemiconductor materials that are layered and patterned onto a substrate,such as silicon, by various process systems. For example, a firstprocess system deposits a layer of material, while another processsystem etches a pattern in such deposited material.

Each process system includes an interface for inputting a recipe forcontrolling the process. The recipe generally includes a plurality ofsetpoints that each specifies an operating parameter value for aparticular device of the process system. For example, a setpoint for achemical vapor deposition (CVD) system may specify a gas flow value fora particular flow control component in the CVD system. Other types ofdevices may include valves, lifts, pedestals, indexers, robots for waferhandling, etc. These devices are given a particular command forperforming an action so as to reach a specified setpoint, and the devicethen automatically performs such action.

It is often desirable to monitor an operating parameter of a processdevice to determine whether it has reached a specified setpoint. Theproblem with providing such a monitoring scheme is that the particularsof a recipe, such as setpoint, are often proprietary. That is, a user ofa process system may set up the process system with a proprietary recipeand then not wish the recipe setpoints to be output from the processsystem, for example, for monitoring purposes by a third party, such asthe process system support personnel.

Accordingly, it would be beneficial to provide a mechanism formonitoring the operation of a process system without requiring knowledgeof the recipe setpoints or any other proprietary information.

SUMMARY OF THE INVENTION

Apparatus and methods for monitoring an operation parameter of a processtool, independently of a process system recipe, are provided. Ingeneral, an indirect effect that results from implementing an event froma process system recipe on the process system is monitored without usingthe specific values or setpoints that are entered for such event intothe process system to thereby change a state of such process system. Inone embodiment, the behavior of a process device as it transitionsbetween different states is monitored for a single cycle of operation orover time to detect trends that indicate a potential failure of theprocess device. When a trend that indicates a potential failure isdetected, an alarm is generated. In one implementation, the time forreaching a particular stage of operation may be repeatedly monitoredover a plurality of device cycles. For example, the time to open a valveor door may be monitored. In another example, the time for reaching astable phase of gas flow after a ramping stage has commenced ismonitored. When the time for reaching a particular stage begins todecline by a predetermined amount, an alarm may be generated.

In one embodiment, a method of monitoring a process system forperforming a fabrication operation on a semiconductor wafer isdisclosed. Feedback specifying a characteristic of a component of theprocess system is received. The characteristic is in response to inputdata sent to the component. It is determined whether there is an actualor imminent problem with the process system based the feedback from suchcomponent. Such determination is accomplished without analysis of theinput data sent to such component. The actual or imminent problem isreported or an alert is sent regarding the actual or imminent problemwhen it is determined that there is an actual or imminent problem.

In a specific implementation, the component is a valve of the processsystem, the feedback specifies the state of the valve, and it isdetermined that there is an actual or imminent problem when the valvehas a delay for transitioning between an open and closed state and suchdelay is greater than a predetermined duration or such delay has a rateof change over time that is greater than a predetermined amount. Inanother implementation, the component is a door of the process system,the feedback specifies the state of the door, and it is determined thatthere is an actual or imminent problem when the door has a delay fortransitioning between an open and closed state that is greater than apredetermined duration or such delay has a rate of change over time thatis greater than a predetermined amount. In yet another implementationexample, the component is a mass flow controller (MFC) or a unitpressure controller (UPC) of the process system, the feedback specifiesthe state of the MFC or UPC, and it is determined that there is anactual or imminent problem when the MFC or UPC has a delay fortransitioning between an idle and stable state and such delay is greaterthan a predetermined duration or such delay has a rate of change overtime that is greater than a predetermined amount. In another aspect, thefeedback specifies an effective orifice diameter of the MFC or UPC, andit is determined that there is an actual or imminent problem when theeffective orifice diameter correlates with probability of failure thatis higher than a predetermined amount.

In another feature, the component is a pedestal or a lift of the processsystem, the feedback specifies the state of the position of the pedestalor lift, and it is determined that there is an actual or imminentproblem when the pedestal or lift has a delay for transitioning betweenan up and down state and such delay is greater than a predeterminedduration or such delay has a rate of change over time that is greaterthan a predetermined amount. In another implementation, the component isa wafer indexer of the process system, the feedback specifies the stateof the position of the indexer, and it is determined that there is anactual or imminent problem when the indexer has a delay fortransitioning between a first and a second position and such delay isgreater than a predetermined duration or a rate of change of such delayover time is greater than a predetermined amount. In another embodiment,the component is a robot arm of the process system, the feedbackspecifies the state of the position of the robot arm, and it isdetermined that there is an actual or imminent problem when the robotarm has a delay for transitioning between a first and a second positionand such delay is greater than a predetermined duration or a rate ofchange of such delay over time is greater than a predetermined amount.In another aspect, the component is a radio frequency (RF) generator ofthe process system, the feedback specifies the state of the RFgenerator, and it is determined that there is an actual or imminentproblem when the RF generator has a delay for transitioning between anon and off state and such delay is greater than a predetermined durationor a rate of change of such delay over time is greater than apredetermined amount.

In a further aspect, an alert regarding the actual or imminent problemis sent when it is determined that there is an actual or imminentproblem, and a shutdown of the process system is scheduled. Wafers arere-routed to another process system. The process system is then examinedto determine a cause of the problem. In another aspect, determiningwhether there is an actual or imminent problem with the process systemis accomplished by correlating the feedback with feedback from othermeasurement devices to thereby predict failure are likely to occur undera set of conditions of the current and other measurement devices.

In another embodiment, the invention pertains to an apparatus formonitoring a process system for performing a fabrication operation on asemiconductor wafer. The apparatus includes one or more processors andone or more memory. At least one of the processors and memory areadapted for performing one or more of the above described methodoperations. In another embodiment, the invention pertains to a computerprogram product for monitoring a process system for performing afabrication operation on a semiconductor wafer. The computer programproduct includes at least one computer readable medium and computerprogram instructions stored within the at least one computer readableproduct configured to cause a processing device to perform one or moreof the above described method operations.

These and other features and advantages of the present invention will bepresented in more detail in the following specification of the inventionand the accompanying figures which illustrate by way of example theprinciples of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention is illustrated by way of example, and not by wayof limitation.

FIG. 1 is a diagrammatic representation of a fabrication facility inaccordance with one embodiment of the present invention.

FIG. 2 is block diagram illustrating how the monitoring system of FIG. 1can be coupled with various components of a particular process tool inaccordance with a specific implementation of the present invention.

FIG. 3A is a diagrammatic representation of a mass flow controller.

FIG. 3B is a diagrammatic representation of a unit pressure controller.

FIG. 3C is a graph of flow rate/pressure as a function of time thatillustrates the various phases of the gas flowing in an MFC or UPC.

FIG. 4 is a flowchart illustrating a procedure for monitoring the timeof one or more Ramping or Shutdown Stages in accordance with oneembodiment of the present invention.

FIG. 5A is a diagrammatic representation of a valve.

FIG. 5B is a diagrammatic representation of a pedestal and lift.

FIG. 5C a graph of position as a function of time that illustrates thevarious states of a valve, pedestal, or lift.

FIG. 6 is a flowchart illustrating a procedure for monitoring theramping delay of a binary state component in accordance with oneembodiment of the present invention.

FIG. 7A is a diagrammatic representation of an RF generator.

FIG. 7B contain block diagrams of an indexer and robot.

FIG. 8 illustrates a typical computer system that, when appropriatelyconfigured or designed, can serve as a monitoring system of thisinvention.

DETAILED DESCRIPTION OF THE INVENTION

Reference will now be made in detail to a specific embodiment of theinvention. An example of this embodiment is illustrated in theaccompanying drawings. While the invention will be described inconjunction with this specific embodiment, it will be understood that itis not intended to limit the invention to one embodiment. On thecontrary, it is intended to cover alternatives, modifications, andequivalents as may be included within the spirit and scope of theinvention as defined by the appended claims. In the followingdescription, numerous specific details are set forth in order to providea thorough understanding of the present invention. The present inventionmay be practiced without some or all of these specific details. In otherinstances, well known process operations have not been described indetail in order not to unnecessarily obscure the present invention.

In this application, the term “wafer” is used extensively and refers toa semiconductor wafer at any stage in the fabrication process. Thediscussion herein focuses on monitoring the health of process systemswhich perform various stages of the fabrication process. Examples ofprocess systems include chemical vapor deposition (CVD) tools such asplasma-enhanced chemical vapor deposition (PECVD) tools or high-densityplasma chemical vapor deposition process (HDP CVD) tools, physical vapordeposition (PVD) tools, ALD (atomic layer deposition) tools,electrochemical deposition (ECD) or electroplating tools, surfacepreparation tools, chemical mechanical (CMP) tools, ultra violet thermalprocessing (UVTP) tools, and etching tools. The invention is not limitedto the specific types of process systems discussed herein however. FIG.1 is a diagrammatic representation of a fabrication facility 100 inaccordance with one embodiment of the present invention. As shown, thefacility 100 includes a plurality of process systems 102 for performinga particular fabrication process on a semiconductor wafer, or the like.Although only three different process systems 102 are illustrated, ofcourse, the facility would typically have different process systemsnumbering in the tens or hundreds. In FIG. 1, the facility 100 includesa PVD tool 102 a for depositing a film, a surface preparation tool 102 bfor stripping photoresist from a wafer or post-process cleaning of awafer, and an electroplating tool 102 c for building copper primaryconduction wires in an integrated circuit.

In the present invention, the facility 100 also includes a monitoringsystem 104 having one or more databases, referred to as a data historian106, for tracking the health of one or more process systems andreporting problems or potential problems with such process systems. Themonitoring system 104 may take the form of a stand alone system (asshown) or be integrated in one or more process tools. A problem orpotential problem may include any aberration which causes (or may cause)damage to a person, product, and/or the process system.

FIG. 2 is a block diagram illustrating how the monitoring system 104 ofFIG. 1 can be coupled with various components 204 of a particularprocess tool 202 in accordance with a specific implementation of thepresent invention. As shown, monitoring system 104 is coupled with thesecomponents 204 through one or more controller(s) 206. Examples ofcomponents include, but are not limited to, mass flow controllers(MFC's), unit pressure controllers (UPC's), temperature controllers,valves, pedestals, lifts, generators, indexers, robots, etc.

The controller(s) may be arranged in any suitable configuration. In oneimplementation, controllers are arranged hierarchically (not shown). Forinstance, a first level of I/O controllers each control and is coupleddirectly to a specific subset of components; a second level of modulecontrollers control are each coupled to one or more I/O controllers; anda top level system controller controls and is coupled directly to all ofthe module controllers.

No matter the particular arrangement of controllers, the controllers aregenerally configured to send commands to control behavior of thecomponents. For example, commands may be sent to close or open a valveor door, raise or lower a pedestal or a lift to an up or down position,cause the pressure or flow rate of a gas to change to a particularsetpoint, cause a robot or indexer to move to a particular position,activate or deactivate an RF (radio frequency) generator to generate ordissipate a plasma, cause a temperature controller to move to aparticular temperature, change a lamp intensity, cause a chamber to bepumped to a vacuum state, initiate a plasma to be generated, initiate aflow (e.g., gas or liquid), set a particular current or voltage, set arotational speed, set a particular pressure, etc. In general, aparticular setpoint is specified to a particular component at aparticular time so as to cause the component to change its state to suchsetpoint. A setpoint generally specifies a specific operation suchsetting the component to one or more particular parameter values and/ora duration of time for such setting. As shown, Setpoint_1 is input tocomponent 204 a; Setpoint_2 is input to component 204 b; and Setpoint_3is input to component 204 c.

While a component is attempting to reach such setpoint, variousoperating parameters may be measured and output from the component tothe monitoring system 104. For example, Operating Parameter1 is outputfrom component 204 a in response to Setpoint_1; Operating Parameter2 isoutput from component 204 b in response to Setpoint_2; OperatingParameter3 is output from component 204 c in response to Setpoint_3. Oneor more operating parameters may be output from a particular componentduring various stages of the system. The operating parameters mayinclude one or more measured values, indicate the time of a particularevent or measurement, and/or specify the particular operational state orphase. A measured value may include pressure, flow rate, temperature,effective orifice diameter, RF or DC power level, a time duration toprocess the wafer, a rotation speed, a voltage or current value, purgetime, pump time, heat time, etc. The following state transitions may beindicated: up, down, open, closed, wafer index, robot arm position, agas stable or idle state, etc. The operating parameters would alsotypically include identifiers for the particular component andprocessing system.

In one implementation, the operating parameters are input to themonitoring system in an event driven manner. That is, operatingparameters are output when a significant event in the component occurs.For example, an event occurs when the measurement device transitions toa new state. The controllers may be operable to detect a new state byanalyzing the measured output's curve shape. For instance, a significantchange in a measured value has occurred after it has leveled off or whenramping has commenced. Alternatively, the monitoring system mayperiodically poll each component for operating parameters or eachcomponent may continuously and periodically output operating parameterswithout being event driven.

In embodiments of the present invention, the operating parameters thatare measured and output from a particular component do not have toinclude the specified setpoints that were input to the particularcomponent. In other words, the monitoring tool does not requireknowledge of the recipe that is used to control the particularcomponents of a particular process system. In a specific embodiment,output of the Setpoint (e.g., from a controller or component) to themonitoring system is disabled.

FIG. 3A is a diagrammatic representation of an MFC 300 that will be usedto describe the basic operation of such component. In general, gas isinput to MFC 300, flows through a sensor 304 and orifice 302, and outputfrom the MFC. The gas flow rate may be controlled by inputting asetpoint specifying a particular flow rate, e.g., standard liters perminute (slm) or standard cubic centimeters per minute (sccm), to theMFC. The setpoint causes the flow rate to change to thereby reach suchsetpoint. For instance, the setpoint input causes the orifice 302 toopen to a wider size or close to a narrower size. The sensor detects thegas flow rate. The MFC also outputs feedback, for example, in the formof a flow rate value. This flow rate may eventually be included in a setof operating parameters, along with a time and state value, to amonitoring system (e.g., 104). The effective orifice diameter may alsobe output from the MFC 300 to the monitoring system.

FIG. 3B is a diagrammatic representation of an UPC 310. Similar to anMFC, gas is input to UPC 310, flows through a sensor 314 and orifice312, and output from the UPC. The gas flow rate may be controlled byinputting a setpoint specifying a particular pressure value, e.g.,pounds per square inch (psi), to the UPC. The setpoint causes thepressure to change by opening or closing the orifice, for example, tothereby reach such setpoint. The UPC also outputs feedback, for example,in the form of a pressure value and perhaps effective orifice diameter.This pressure value (and effective orifice diameter) may also eventuallybe included in a set of operating parameters, along with a time andstate value, to a monitoring system (e.g., 104).

An MFC or UPC may be used to input gas into a chamber for a vapordeposition process. The gas may interact with a plasma or heat tothereby cause a film of material to form on a wafer or cause a film tobe removed from a wafer. Input of a particular setpoint to an MFC or UPCcauses the gas to transition between two different phases or stages ifthe MFC or UPC is functioning properly. FIG. 3C is a graph of flowrate/pressure as a function of time that illustrates the various phasesof the gas flowing in an MFC or UPC. The Idle Stage 320 occurs whenminimum gas is flowing or moving through the MFC or UPC so as to inhibitmaterial deposition on the wafer. A setpoint is then input to the MFC orUPC at time 322 to cause the orifice of the MFC or UPC to widen, whichcauses the gas flow/pressure to ramp up in a Ramping Stage 324. Once thesetpoint is substantially reached at time 325, the gas has reached aStable Stage 326. For example, when the measured flow rate or pressureis within a predetermined amount from the input setpoint or when theflow rate has increased and then leveled off for a predetermined time,the Stable Stage is reached. At time 328, a shutdown command or setpointis input to the MFC or UPC to cause the gas to ramp down (e.g., theorifice is narrowed) in a Shutting Down Stage 330 until an Idle Stage322 is again reached.

Various aspects of an MFC or UPC may be monitored without requiringknowledge of the setpoint or recipe for the associated process system.That is, the monitoring does not analyze or use the recipe. In oneexample implementation, the effective orifice diameter may be monitored,correlated to failure probability values, and an alert generated whenthe effective orifice diameter correlates to a particular failureprobability. In another example illustrated in FIG. 4, the time it takesfor the MFC or UPC to ramp up or shut down is monitored. A long durationfor a single occurrence of such stage or a trend towards increasingdurations for such stage may indicate a failure or that a failure isimminent and, accordingly, an alarm may be sent or the discrepancy maybe stored or reported.

FIG. 4 is a flowchart illustrating a procedure 400 for monitoring thetime of one or more Ramping or Shutdown Stages in accordance with oneembodiment of the present invention. Initially, it may be determinedwhether a change in phase or stage has occurred in operation 402. In anevent driven implementation, the following transitions may correspond toa phase change and be so specified to the monitoring system: transitionfrom idle to ramping phase, (ii) transition from ramping to stablephase, (iii) transition from stable to shutting down phase, and (iv)transition from shutting down phase to idle phase. Each of thesetransition changes may result in such transition and its time ofoccurrence being specified to the monitoring system, for example, by acontroller.

If no change has occurred, the procedure may continue to wait for aphase change. When a change occurs, it may then be determined whethersuch change corresponds to the start of either a ramping or shuttingdown phase in operation 404. For instance, these two transitions triggera monitoring procedure in embodiments of the present invention. Ofcourse, other transitions or aspects of each phase may also bemonitored. For instance, the pressure or flow rate may be comparedagainst the input setpoint during the stable phase.

In the illustrated example, if a ramping or shutting down phase has notstarted, the procedure may continue to wait for another change inoperation 402. When a ramping or shut down phase has commenced, the timefor the start of such phase is stored, for example, in data historian106 in operation 406. It may then be determined whether the stable phasehas been reached after the ramping phase has commenced or whether theidle phase has been reached after the shutting down phase has commencedin operation 408.

If the stable phase is not reached after commencement of the rampingphase or the idle phase is not reached after commencement of theshutting down phase, it may then be determined whether the delay hasreached a predetermined duration of time in operation 414. This step maybe performed to check whether the ramping or shutting down phase istaking an unacceptable amount of time. An “unacceptable amount of time”may be defined in any suitable manner and may correlate to a maximumtime that has been experienced for reaching the stable or idle phaseduring past process cycles. If this predetermined delay limit has notbeen reached, the procedure continues to wait for the stable or idlephase in operation 408. Otherwise, if the limit has been reached, areport of the error may be generated and/or an alarm may be sent inoperation 412.

When the delay is larger than a predetermined limit, this discrepancybetween the ramping or shutting down delay and the predetermined limitmay simply be reported or stored so that it can be reviewed later by auser. An alarm may also be sent and include any suitable information,such as the recent history of phase and corresponding time changes,identification of the component and process system, etc. An alarm may begenerated in any suitable manner. By way of examples, an error messagemay be displayed on the graphical user interface of the process systemand/or monitoring system and/or an email, instance message, telephonetext or voice message, and/or page may be sent to one or more particularpersonnel.

If the stable phase is reached after commencement of the ramping phaseor the idle phase is reached after commencement of the shutting downphase, a delay between the start of the ramping or shutting down phaseand the commencement of either the stable or idle phase may bedetermined and a rate of change of the current and previously determineddelays may also be determined in operation 407. The determined currentdelay and rate of change of the delays may also be stored in operation407.

It may then be determined whether the delay for the ramping or shuttingdown phase is greater than a predetermined duration of time in operation410. This limit may be set to correlate with time delays that havepreviously resulted in failure on the wafer or damage to the processsystem, product or a human. If the delay is longer than thepredetermined duration of time, an error may be reported and/or an alarmsent in operation 412.

If the current delay is found not to be above a predetermined limit, itmay also then be determined whether the rate of change in the delay isgreater than a predetermined amount in operation 416. In other words, itis determined whether the delay of the ramping or shutting down phase isincreasing over time by a significant amount. The significant amount canbe any specified value that correlates with a high probability of aproblem occurring. If the rate of change in delay is above apredetermined amount, an error may be reported or an alarm sent inoperation 412. Otherwise, the procedure may continue to wait for anotherphase change in operation 402.

A significant delay or increase in the delay in the ramping up time foran MFC or UPC can indicate various problems. One problem may involve afluxuation in the pressure in the gas input into the MFC or UPC. Theorifice may become starved and not be receiving enough gas to produce aparticular flow rate or pressure, even when the orifice is at a maximumopening. There may be problem upstream in the gas line, e.g., a clog,leak, or excess load sharing by other systems. Another problem may occurdownstream from the MFC or UPC when excess gas is backing up into theorifice and causing too much back pressure to achieve a particular flowrate through the MFC or UPC.

In another monitoring example, the effective orifice diameter of the MFCor UPC may be checked while the gas is flowing normally to determinewhether it is in a “normal” position. The “normal” position may bedetermined by examining long term correlations between effective orificediameter and failure probability. If the effective orifice diameter isdetermined to correlate to a high failure probability, and an error maybe reported or an alarm sent.

FIG. 5A is a diagrammatic representation of a valve 510. The valvereceives input, which is output when the valve is open. The valve iscontrolled by a setpoint that specifies that the valve be closed oropened. The valve also outputs feedback to indicate the valve's state(e.g., open or closed). FIG. 5B is a diagrammatic representation of apedestal 520 and lift 530. The lift also includes lift pins 534 thatraise the wafer 524 to an up position that is above the platform 524 andto a down position that rests the wafer on the platform 524. Both thepedestal and lift include a platform 524 upon which the wafer resides, ashaft 526 upon which the platform is coupled, and a motor 528 for movingthe platform or lift pins, along with the wafer 522, to an up and downposition. The pedestal 520 is operable to move the platform 524 andwafer along direction 525 to an up or down position, while the lift 530is operable to move the pins 534 and wafer along direction 532 to an upor down position.

FIG. 5C a graph of position as a function of time that illustrates thevarious states of a valve, pedestal, or lift. The Down or Closed state540 occurs when the pedestal or lift is in a down position or when thevalve is closed. A setpoint is then input to the valve, pedestal, orlift at time 550, which causes (in most cases) the pedestal or lift orthe valve to ramp up to an up or an open position in a Ramping Up State542. That is, the Ramping Up State corresponds to the transition timebetween an Down/Closed State to an Up/Open State. Once the pedestal orlift is in an up position or the valve is open at time 552, thecomponent has reached an UP or Open State 544. At time 554, a “Down” or“Close” command or setpoint is input to the pedestal/lift or valve,respectively, to cause the component to ramp down in a Ramping DownState 546 until a Down/Closed State 548 is reached at time 556. Thisgraph is also representative of other types of binary state devices,such as doors.

In general, the transition delay between the two states of a binary typecomponent can be monitored without requiring analysis of a recipe. FIG.6 is a flowchart illustrating a procedure 600 for monitoring the rampingdelay of a binary state component in accordance with one embodiment ofthe present invention. Initially, the procedure awaits a change in statein operation 602. A state change can include a change from an up or downstate to a ramping state or a change from an open or closed state to aramping state. The time for the start of this new (e.g., ramping) stateis then stored in operation 606.

After a state change occurs (e.g., ramping has commenced), it may thenbe determined whether another change in state has occurred in operation608. That is, it is determined whether the ramping state has ended andthe component has changed between a ramping state to an up/down state orbetween ramping state to an open/closed state. If another state changehas occurred, a delay between each state may be determined and a rate ofchange of the current and previously determined delays may also bedetermined in operation 607. It may then be determined whether thecurrent delay is longer than a predetermined duration of time inoperation 610. If the delay is longer than the predetermined duration oftime, an error may be reported and/or an alarm sent in operation 612.

If the current delay is found not to be above a predetermined limit, itmay also then be determined whether the rate of change in the delay isgreater than a predetermined amount in operation 616. In other words, itis determined whether the delay of the ramping state is increasing overtime by a significant amount. The significant amount can be anyspecified value that correlates with a high probability of a problemoccurring. If the rate of change in delay is above a predeterminedamount, an error may be reported and/or an alarm sent in operation 612.Otherwise, the procedure may continue to wait for another state changein operation 602.

If another state change has not occurred, it may then be determinedwhether the current delay for reaching another state has surpassed apredetermined duration of time in operation 614. For instance, it may betaking a significant time for the valve to open or the pedestal/lift tomove to an up position. If this predetermined delay limit has not beenreached, the procedure continues to wait for the next state change inoperation 608. Otherwise, if the limit has been reached, a report of theerror may be generated and/or an alarm may be sent in operation 612.

A significant delay in opening/closing a valve or door or moving apedestal or lift may indicate wear and tear on the component. Wornmechanical parts may result in particles being introduced onto thesemiconductor device. Particle contamination of the device can result indevice failure. A significant delay may also indicate that pressure isbeing built up behind a valve or door that is blocked and may cause suchhigh pressure to break the current or another valve in the system, forexample.

Another type of component is an RF generator which is operable to createa plasma of ionized gas from an RF field. FIG. 7A is a diagrammaticrepresentation of an RF generator 700. A setpoint is used to turn on theRF generator to thereby create an RF field that is strong enough to thenbreak apart atoms in a gas that is present near the generator and createan ionized plasma. The states of the RF generator can include an idlestate, a ramping up state, a stable state, and a shutting down state.These states are similar to the states of an MFC or UPC, but havesharper ramping down and shutting down states. These states may beoutput from the RF generator or determined by a controller coupled tothe RF generator which is operable to send the setpoint to the RFgenerator and receive feedback from the RF generator. The feedback mayinclude measurements of forward power, reflected power, and load. Theload may be derived from the other two measurements. These measurementsand the states of the RF generator may be monitored, for example, by amonitoring system.

Embodiments of the present invention include techniques for monitoringthe delay of the ramping up and shutting down states for an RFgenerator, or the like. If the ramping up state takes an inordinateamount of time, there could be a problem with the generator, e.g., notenough gas, bad ground plane, power is coupled to the wrong input,mismatched frequency inputs, etc. A long delay could also mean that theenvironment into which the plasma is being built is not ideal.

Other types of components include an indexer and robot, which areillustrated in FIG. 7B. As shown, an indexer 710 is operable to move acassette of wafers 711 up and down along axis 712. The wafers arestacked vertically in the cassette so that vertical movement results indifferent wafers being positioned at a particular position. As shown,the cassette of wafers 711 is moved along direction 712 so as toposition a particular one of the wafers (or wafer slot) at position A.For instance, the wafers may include wafers or slots 1 through 25. Theindexer may position wafer 1 at position A, and then wafer 2 at positionA, etc. As shown, position A is reachable by an arm 715 of robot 714,which is configured to move the wafer at position A to another position,e.g., position B.

In sum, the indexer moves a particular wafer slot to a position that isaccessible by a robot arm. Accordingly, feedback from an indexer may bein the form of position value. This position value may correspond toparticular wafer slots. The transition time between slots may bemonitored to ensure that the indexer is not taking more than apredetermined delay in moving to between particular wafer slots. A longdelay may indicate that the indexer has experienced wear and tear orthere is a problem with an electrical component of the indexer. As withany component, wear and tear on a mechanical component can produceparticles and destroy the wafer product.

Each arm position of each robot may also be monitored for delays betweenparticular positions. Each process system may include one or more robotsthat each have one or more arms for moving wafers between loadingcassettes and chambers of the process system. Each arm may be operableto rotationally or linearly move between each position. As shown, arm715 of robot 714 moves a wafer between position A of cassette 711 andposition B of chamber 716. The transition time between a set ofpositions may be monitored for significant delays that may indicate aproblem with the robot or process system environment.

In any of the above described monitoring examples, if an alert is sentfor any type of component of a particular process tool, downtime of theprocess tool may then be scheduled. In contrast to scheduled downtime,unscheduled downtime is associated with significant expenditures of timeand money. In a scheduled shutdown, wafers can be re-routed to othertools, rather than scrapped. The monitoring techniques of the presentinvention allow detection of actual failures, as well as prediction ofpotential failures. When a failure has occurred or is predicted tolikely occur, the process system may be examined to determine a rootcause of the failure or potential failure. For instance, when a door orvalve is taking longer to open, the door or valve may be examined forwear and tear.

The characteristics, such as ramping delay, of subsets of components ofa process system may also be correlated together to predict failuresthat occur when a particular subset of conditions are present. Forinstance, if a particular set of characteristic values occur together,this behavior can be correlated with a particular failure outcome. Stepscan then be taken to alleviate the problem.

The monitoring techniques of the present invention may be implemented inany suitable combination of software and/or hardware system, such as ametrology or inspection system's processor. Regardless of the system'sconfiguration, it may employ one or more memories or memory modulesconfigured to store data, program instructions for the general-purposemetrology operations and/or the inventive techniques described herein.The program instructions may control the operation of an operatingsystem and/or one or more applications, for example. The memory ormemories may also be configured to store setpoints, feedbackinformation, specification information, etc.

Because such information and program instructions may be employed toimplement the systems/methods described herein, the present inventionrelates to machine readable media that include program instructions,state information, etc. for performing various operations describedherein. Examples of machine-readable media include, but are not limitedto, magnetic media such as hard disks, floppy disks, and magnetic tape;optical media such as CD-ROM disks; magneto-optical media such asfloptical disks; and hardware devices that are specially configured tostore and perform program instructions, such as read-only memory devices(ROM) and random access memory (RAM). The invention may also be embodiedin a carrier wave traveling over an appropriate medium such as airwaves,optical lines, electric lines, etc. Examples of program instructionsinclude both machine code, such as produced by a compiler, and filescontaining higher level code that may be executed by the computer usingan interpreter.

Embodiments of the present invention employ various processes involvingdata stored in or transferred through one or more computer systems.Embodiments of the present invention also relate to the apparatus forperforming these operations. These apparatus and processes may beemployed to monitor characteristics of one or more components, retrievestored specifications from databases or other repositories, and comparesuch monitored characteristics to the specifications. The monitoringapparatus of this invention may be specially constructed for therequired purposes, or it may be a general-purpose computer selectivelyactivated or reconfigured by a computer program and/or data structurestored in the computer. The processes presented herein are notinherently related to any particular computer or other apparatus. Inparticular, various general-purpose machines may be used with programswritten in accordance with the teachings herein, or it may be moreconvenient to construct a more specialized apparatus to perform therequired method steps.

FIG. 8 illustrates a typical computer system that, when appropriatelyconfigured or designed, can serve as a monitoring system of thisinvention. The computer system 800 includes any number of processors 802(also referred to as central processing units, or CPUs) that are coupledto storage devices including primary storage 806 (typically a randomaccess memory, or RAM), primary storage 804 (typically a read onlymemory, or ROM). CPU 802 may be of various types includingmicrocontrollers and microprocessors such as programmable devices (e.g.,CPLDs and FPGAs) and unprogrammable devices such as gate array ASICs orgeneral purpose microprocessors. As is well known in the art, primarystorage 804 acts to transfer data and instructions uni-directionally tothe CPU and primary storage 806 is used typically to transfer data andinstructions in a bi-directional manner. Both of these primary storagedevices may include any suitable computer-readable media such as thosedescribed above. A mass storage device 808 is also coupledbi-directionally to CPU 802 and provides additional data storagecapacity and may include any of the computer-readable media describedabove. Mass storage device 808 may be used to store programs, data andthe like and is typically a secondary storage medium such as a harddisk. It will be appreciated that the information retained within themass storage device 808, may, in appropriate cases, be incorporated instandard fashion as part of primary storage 806 as virtual memory. Aspecific mass storage device such as a CD-ROM 814 may also pass datauni-directionally to the CPU.

CPU 802 is also coupled to an interface 810 that connects to one or moreinput/output devices such as such as video monitors, track balls, mice,keyboards, microphones, touch-sensitive displays, transducer cardreaders, magnetic or paper tape readers, tablets, styluses, voice orhandwriting recognizers, or other well-known input devices such as, ofcourse, other computers. Finally, CPU 802 optionally may be coupled toan external device such as a database or a computer ortelecommunications network using an external connection as showngenerally at 812. With such a connection, it is contemplated that theCPU might receive information from the network, or might outputinformation to the network in the course of performing the method stepsdescribed herein.

Typically, the computer system 800 is coupled with various one or morecontrollers and measurements devices of one or more process systems. Forexample, the computer system of FIG. 8 may correspond to the monitoringsystem 104 depicted in FIGS. 1 and 2. Data from each component 204 ofeach process system is provided for analysis by system 800. With thisdata, the apparatus 800 can issue various reports and alarms when thedata is determined to be out of specification, e.g., indicates orpredicts a potential problem or failure.

Although the foregoing invention has been described in some detail forpurposes of clarity of understanding, it will be apparent that certainchanges and modifications may be practiced within the scope of theappended claims. Therefore, the described embodiments should be taken asillustrative and not restrictive, and the invention should not belimited to the details given herein but should be defined by thefollowing claims and their full scope of equivalents.

What is claimed is:
 1. A method of monitoring a process system forperforming a fabrication operation on a semiconductor wafer, the methodcomprising: enabling output of a feedback from the process system andreceiving the feedback, the feedback specifying a characteristic of acomponent of the process system, wherein the characteristic is inresponse to input data sent to the component; determining whether thereis an actual or imminent problem with the process system based on thefeedback, wherein such determination is accomplished without analysis ofthe input data sent to such component; and reporting the actual orimminent problem or sending an alert regarding the actual or imminentproblem when it is determined that there is an actual or imminentproblem, while physically disabling output of the input data from theprocess system.
 2. A method as recited in claim 1, wherein the componentis a mass flow controller (MFC) or a unit pressure controller (UPC) ofthe process system, the feedback specifies an effective orifice diameterof the MFC or UPC, and it is determined that there is an actual orimminent problem when the effective orifice diameter correlates withprobability of failure that is higher than a predetermined amount.
 3. Amethod as recited in claim 1, wherein determining whether there is anactual or imminent problem with the process system is accomplished bycorrelating the feedback with feedback from other measurement devices tothereby predict failure are likely to occur under a set of conditions ofthe current and other measurement devices.
 4. A method as recited inclaim 1, wherein the feedback specifies an RF power level or DC powerlevel output and the determination is based on such output without beingbased on a RF or DC power level input to the component.
 5. A method asrecited in claim 1, wherein the feedback specifies a length of time ofprocessing the wafer.
 6. A method as recited in claim 1, wherein thefeedback specifies a flow level output and the determination is based onsuch output without being based on a flow level setpoint input to thecomponent.
 7. A method as recited in claim 1, wherein the feedbackspecifies a rotational speed.
 8. A method as recited in claim 1, whereinthe feedback specifies a voltage output.
 9. An apparatus for monitoringa process system for performing a fabrication operation on asemiconductor wafer, comprising: one or more processors; one or morememory, wherein at least one of the processors and memory are adaptedfor: enabling output of a feedback from the process system and receivingthe feedback, the feedback specifying a characteristic of a component ofthe process system, wherein the characteristic is in response to inputdata sent to the component; determining whether there is an actual orimminent problem with the process system based on the feedback, whereinsuch determination is accomplished without analysis of the input datasent to such component; and reporting the actual or imminent problem orsending an alert regarding the actual or imminent problem when it isdetermined that there is an actual or imminent problem, while physicallydisabling output of the input data from the process system.
 10. Anapparatus as recited in claim 9, wherein the component is a mass flowcontroller (MFC) or a unit pressure controller (UPC) of the processsystem, the feedback specifies an effective orifice diameter of the MFCor UPC, and it is determined that there is an actual or imminent problemwhen the effective orifice diameter correlates with probability offailure that is higher than a predetermined amount.
 11. An apparatus asrecited in claim 9, wherein determining whether there is an actual orimminent problem with the process system is accomplished by correlatingthe feedback with feedback from other measurement devices to therebypredict failure are likely to occur under a set of conditions of thecurrent and other measurement devices.
 12. An apparatus as recited inclaim 9, wherein the feedback specifies an RF power level or DC powerlevel output and the determination is based on such output without beingbased on a RF or DC power level input to the component.
 13. An apparatusas recited in claim 9, wherein the feedback specifies a length of timeof processing the wafer.
 14. An apparatus as recited in claim 9, whereinthe feedback specifies a flow level output and the determination isbased on such output without being based on a flow level setpoint inputto the component.
 15. An apparatus as recited in claim 9, wherein thefeedback specifies a rotational speed.
 16. An apparatus as recited inclaim 9, wherein the feedback specifies a voltage output.
 17. A computerprogram product for monitoring a process system for performing afabrication operation on a semiconductor wafer, the computer programproduct comprising: at least one non-transitory computer readablemedium; computer program instructions stored within the at least onecomputer readable product configured to cause a processing device to:enabling output of a feedback from the process system and receiving thefeedback, the feedback specifying a characteristic of a component of theprocess system, wherein the characteristic is in response to input datasent to the component; determining whether there is an actual orimminent problem with the process system based on the feedback, whereinsuch determination is accomplished without analysis of the input datasent to such component; and reporting the actual or imminent problem orsending an alert regarding the actual or imminent problem when it isdetermined that there is an actual or imminent problem, while physicallydisabling output of the input data from the process system.
 18. Acomputer program product as recited in claim 17, wherein the componentis a mass flow controller (MFC) or a unit pressure controller (UPC) ofthe process system, the feedback specifies an effective orifice diameterof the MFC or UPC, and it is determined that there is an actual orimminent problem when the effective orifice diameter correlates withprobability of failure that is higher than a predetermined amount.
 19. Acomputer program product as recited in claim 17, wherein the feedbackspecifies an RF power level or DC power level output and thedetermination is based on such output without being based on a RF or DCpower level input to the component.
 20. A computer program product asrecited in claim 17, wherein the feedback specifies a flow level outputand the determination is based on such output without being based on aflow level setpoint input to the component.
 21. The method of claim 1,wherein the input data includes proprietary input data, and whereindisabling output of the input data includes disabling output of theproprietary input data.
 22. The apparatus of claim 9, wherein the inputdata includes proprietary input data, and wherein disabling output ofthe input data includes disabling output of the proprietary input data.23. The computer program product of claim 17, wherein the input dataincludes proprietary input data, and wherein disabling output of theinput data includes disabling output of the proprietary input data.